A particular kind of apparatus, such as described in U.S. Pat. No. 5,788,827 of Munson, has been used in commerce for removing very fine particles from non-conductive liquids, such as lubricating oil used in large machines. The process carried out by the apparatus involves dividing a liquid stream into two portions, and contacting the portions respectively with high voltage positive and negative electrodes, so that the particles become charged. Then, the liquid stream portions are re-combined, and the particles agglomerate, making them much easier to remove by downstream depth filtration.
There is a continuing desire to improve the performance of the foregoing kind of apparatus, and to provide apparatus which is more easily and economically constructed than in the past.